Optical information recording medium and information recording method

ABSTRACT

An optical information recording medium having, on a substrate, a recording layer capable of recording information by irradiation with laser rays. The recording layer includes a 1,2,3-triazole compound that is not a condensate with 1,3-dimethylbarbituric acid. Also, an information recording method in which such an optical information recording medium is irradiated with a laser having a wavelength of 550 nm or less to record information.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an optical information recordingmedium and an information recording method and in particular to anoptical information recording medium and an information recording methodcapable of recording and reproducing information by irradiation withlaser rays. In particular, the present invention relates to an opticalinformation recording medium suitable for recording information byirradiation with short-wavelength laser rays having wavelengths of 550nm or less and an information recording method using this opticalinformation recording medium.

[0003] 2. Description of the Related Art

[0004] Heretofore, an optical information recording medium (opticaldisk) capable of recording information only once by laser rays has beenknown. This optical disk is also called addition writing-type CD(so-called CD-R), and this disk is structured typically by laminating arecording layer containing an organic colorant, a light-reflective layerconsisting of a metal such as gold, and a protective layer made of resinin this order on a transparent disk-shaped substrate. Recording ofinformation on this CD-R is conducted by irradiating the CD-R withnear-infrared laser rays (usually laser rays with wavelengths in thevicinity of 780 nm), and the portion thus irradiated absorbs the rays toincrease temperature locally thus undergoing a physical or chemicalchange (e.g., formation of pits) thereby changing the opticalcharacteristics at that portion to record information. Reading(reproduction) of information is conducted by irradiating the CD-R withlaser rays having the same wavelength as that of the recording laserrays and detecting a difference in reflectance between a portion wherethe optical characteristics of the recording layer were changed(recorded portion) and a portion where the characteristics were notchanged (unrecorded portion).

[0005] Further, an optical disk called an addition writing-type digitalversatile disk (so-called DVD-R) has been proposed and practically usedas an optical information recording medium capable of higher densityrecording than CD-R. Usually, a DVD-R has either: a structure in whichtwo disks each consisting of a recording layer containing an organicpigment, a light-reflective layer and a protective layer laminated inthis order on a transparent disk-shaped substrate are laminated withtheir recording layers inside; or a structure in which said disk and adisk-shaped protective substrate of the same shape as said disk arelaminated with the recording layer inside. On the transparentdisk-shaped substrate, a guide groove (pre-groove) for trackingirradiation laser rays is formed with a groove width (0.74 to 0.8 μm)which is less than half the width of grooves on a CD-R. Recording andreproduction of information on the DVD-R is performed by irradiation ofvisible laser rays (usually, laser rays having wavelengths in the rangeof 630 nm to 680 nm) to achieve higher density recording than CD-Rs.

[0006] Recently, high-vision TV, networks such as the Internet and thelike have been rapidly spreading. Further, the start of broadcasting ofHDTV (high definition television) is near at hand. Under thesecircumstances, there is a strong demand for a high-capacity recordingmedium capable of recording image information easily and inexpensively.At present, DVD-R fulfills a satisfactory role as a high-capacityrecording medium, but there is an increasing demand for higher capacityand higher density, and development of a recording medium for copingwith such demand is also necessary. Accordingly, a recording medium ofhigher capacity capable of high-density recording with rays of shorterwavelengths than those for DVD-R is being developed.

[0007] For example, Japanese Patent Application Laid Open (JP-A) No.4-74690, JP-A 8-127174, JP-A 11-53758, JP-11-334204, JP-A 11-334205,JP-A 11-334206, JP-A 11-334207, JP-A 2000-43424, JP-A 2000-108513, JP-A2000-113504, JP-A 2000-149320 and JP-A 2000-158818 disclose a recordingand reproduction method wherein an optical information recording mediumhaving a recording layer containing an organic dye is irradiated with alaser having a wavelength of 530 nm or less in a direction from therecording layer toward the light-reflective layer, thus effectingrecording and reproduction of information. In this method, an opticaldisk equipped with a recording layer containing a porphyrin compound, anazo type dye, a metal azo type dye, a quinophthalone type dye, atrimethine cyanine dye, a dicyanovinyl phenyl skeleton dye, a coumarincompound or the like is irradiated with a lasers of blue color(wavelengths of 430 nm and 488 nm) or bluish-green color (wavelength of515 nm), thereby effecting the recording and reproduction ofinformation.

[0008] However, investigations by the inventors of the present inventionhave revealed that the optical disks described in the above publicationscannot achieve practically required sensitivity in the case of recordinginformation by irradiation with short-wavelength laser rays, withwavelengths of 550 nm or less, and other recording characteristics suchas reflectance and degree of modulation are not satisfactory, thusnecessitating further improvements. In particular, the optical disksdescribed in the above publications have lower recording characteristicswhen irradiated with laser rays having wavelengths of 450 nm or less.

SUMMARY OF THE INVENTION

[0009] The present invention was made in view of the problems in theprior art described above, and a first object of the present inventionis to provide an optical information recording medium excellent inrecording characteristics and capable of recording and reproducinginformation by irradiation with laser rays having wavelengths of 550 nmor less, particularly laser rays having wavelengths of 450 nm or less,which are shorter than wavelengths of laser rays used in recording andreproducing information on CD-R and DVD-R. A second object of thepresent invention is to provide an information recording method capableof high-density recording of information by irradiation with laser rayshaving wavelengths of 550 nm or less, particularly laser rays havingwavelengths of 450 nm or less, which are shorter than wavelengths oflaser rays used in recording and reproduction on CD-R and DVD-R. A firstaspect of the present invention is directed to an optical informationrecording medium having: a substrate; and a recording layer on thesubstrate which is capable of recording information by irradiation withlaser rays, the recording layer comprising a 1,2,3-triazole compounddevoid of a condensate with 1,3-dimethylbarbituric acid. The secondaspect of the present invention is directed to an information recordingmethod including steps of: providing an optical information recordingmedium having, on a substrate, a recording layer capable of recordinginformation by irradiation with laser rays, the recording layercomprising a 1,2,3-triazole compound devoid of a condensate with1,3-dimethylbarbituric acid; and irradiating the optical informationrecording medium with a laser having a wavelength of at most 550 nm forrecording information.

[0010] According to the present inventors' studies, an opticalinformation recording medium having a recording layer on a substrate,which has good recording characteristics in having high sensitivity,high reflectance and high degrees of modulation even with respect toshort-wavelength laser rays having wavelengths of 550 nm or less, andparticularly wavelengths of 450 nm or less, can be obtained by inclusionof a 1,2,3-triazole compound in the recording layer, which is capable ofrecording information by irradiation with laser lays. Further, thisoptical information recording medium is capable of high-densityrecording of information by irradiation with laser rays havingwavelengths of 550 nm or less, and particularly wavelengths of 450 nm orless.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Below, the embodiments of the optical information recordingmedium and the information recording method according to the presentinvention are described in detail.

[0012] The optical information recording medium of the present inventionis a medium having, on a substrate, a recording layer capable ofrecording information by irradiation with laser rays. The recordinglayer contains a 1,2,3-triazole compound (not a condensate with1,3-dimethylbarbituric acid). Condensates with 1,3-dimethylbarbituricacid are excluded because condensates with 1,3-dimethylbarbituric acidhave a problem of easy crystallization, such that upon application forforming a recording layer, the recording layer tends to be made opaque.

[0013] The 1,2,3-triazole compound used in the optical informationrecording medium of the present invention is preferably a compoundrepresented by the following general formula (I):

[0014] in which: A and B represent optionally substituted aromaticrings; m and n each independently represents an integer from 1 to 3; R¹and R² represent substituents (the substituent represented by R¹ is notderived from 1,3-dimethylbarbituric acid); and p and q representintegers from 0 to 3.

[0015] The 1,2,3-triazole compounds represented by the general formula(I) are compounds wherein the aromatic ring represented by B issubstituted at least with a hydroxyl group and a nitrogen atom at the2-position in a 1,2,3-triazolyl group, and the aromatic grouprepresented by A forms a fused ring with the 1,2,3-triazole ring.

[0016] In the general formula (I), m is a number of 1,2,3-triazolylgroups. m is an integer from 1 to 3, preferably 1 or 2, and particularlypreferably 2. n is a number of hydroxyl groups. n is an integer from 1to 3, and preferably equals to m.

[0017] In the general formula (I), examples of the optionallysubstituted aromatic rings represented by A and B include hydrocarbonaromatic rings such as a benzene ring, naphthalene ring, anthracene ringand phenanthrene ring and heterocyclic aromatic rings such as a pyridinering, pyrimidine ring, quinoline ring, furan ring, pyrrole ring andpyrazol ring, among which the benzene ring, naphthalene ring andpyridine ring are preferable, and the benzene ring is particularlypreferable.

[0018] In the general formula (I), R¹ is a substituent on the aromaticring represented by B, and R² is a substituent on the aromatic ringrepresented by A. p is a number of substituent R¹ groups. p is aninteger from 0 to 3, preferably 1 or 2, and particularly preferably 1. qis a number of substituent R² groups. q is an integer from 0 to 3,preferably 1 or 2, and particularly preferably 1.

[0019] In the general formula (I), examples of the substituentsrepresented by R¹ and R² include a C₁₋₂₀ linear or cyclic alkyl group(e.g., methyl, ethyl, isopropyl, or cyclohexyl), a C₆₋₁₈ aryl group(e.g., phenyl or chlorophenyl, 2,4-di-t-aminophenyl, or 1-naphthyl), aC₇₋₁₉ aralkyl group (e.g., benzyl or anisyl), a C₂₋₂₀ alkenyl group(e.g., vinyl or 2-methylvinyl), a C₂₋₂₀ alkynyl group (e.g., ethynyl,2-methylethynyl, or 2-phenylethynyl), a halogen atom (e.g., F, Cl, Br,or I), a cyano group, a hydroxyl group, a carboxyl group, a C₂₋₂₀ acylgroup (e.g., acetyl, benzoyl, salicyloyl, or pivaloyl), a C₁₋₂₀ alkoxygroup (e.g., methoxy, butoxy, or cyclohexyloxy), a C₆₋₂₀ aryloxy group(e.g., phenoxy, 1-naphthoxy, or toluoyl), a C₁₋₂₀ alkylthio group (e.g.,methylthio, butylthio, benzylthio, or 3-methoxypropylthio), a C₆₋₂₀arylthio group (e.g., phenylthio or 4-chlorophenylthio), a C₁₋₂₀alkylsulfonyl group (e.g., methane sulfonyl or butane sulfonyl), a C₆₋₂₀arylsulfonyl group (e.g., benzene sulfonyl or p-toluene sulfonyl), aC₁₋₁₇ carbamoyl group (e.g., unsubstituted carbamoyl, methyl carbamoyl,ethyl carbamoyl, n-butyl carbamoyl, or dimethyl carbamoyl), a C₀₋₁₆sulfamoyl group (e.g., unsubstituted sulfamoyl, N,N-dipropylsulfamoyl,N-methylsulfamoyl, N-phenylsulfamoyl), a C₁₋₁₆ amide group (e.g.,acetamide or benzamide), a C₂₋₂₀ acyloxy group (e.g., acetoxy orbenzoyloxy), a C₂₋₂₀ alkoxycarbonyl group (e.g., methoxycarbonyl orethoxycarbonyl), a 5- or 6-membered heterocyclic group (e.g., anaromatic heterocyclic ring such as pyridyl, thienyl, furyl, thiazolyl,imidazolyl or pyrazolyl, or a heterocyclic ring such as a pyrrolidinering, piperidine ring, morpholine ring, pyran ring, thiopyran ring,dioxane ring or dithiolan ring). However, groups derived from1,3-dimethylbarbituric acid are excluded from the substituentrepresented by R¹.

[0020] The substituent represented by R¹ is preferably a C₂₋₁₆ linear orcyclic alkyl group, a C₆₋₁₄ aryl group, a C₇₋₁₅ aralkyl group, a C₁₋₁₆alkoxy group, a C₆₋₁₄ aryloxy group, a C₂₋₂₁ acyloxy group, a C₂₋₁₆ acylgroup, a halogen atom, a C₂₋₁₇ alkoxycarbonyl group, a C₁₋₁₀ carbamoylgroup or a C₁₋₁₀ amide group, more preferably a C₂₋₁₀ linear or cyclicalkyl group, a C₇₋₁₃ aralkyl group, a C₆₋₁₀ aryl group, a C₂₋₁₀ alkoxygroup, a C₂₋₁₇ acyloxy group, a C₆₋₁₀ aryloxy group, a chlorine atom, aC₂₋₁₁, alkoxycarbonyl group, a C₂₋₇ carbamoyl group or a C₂₋₈ amidegroup, and particularly preferably a C₃₋₁₀ linear branched or cyclicalkyl group, a C₇₋₁₁ aralkyl group, a C₂₋₈ alkoxy group, a C₂₋₁₁ acylgroup, a C₃₋₉ alkoxycarbonyl group, phenyl or a chlorine atom.

[0021] The substituent represented by R² is preferably a C₁₋₁₆ linear orcyclic alkyl group, a C₆₋₁₄ aryl group, a C₇₋₁₅ aralkyl group, a C₁₋₁₆alkoxy group, a C₆₋₁₄ aryloxy group, a C₂₋₂₁ acyloxy group, a C₁₋₁₆alkylthio group, a C₆₋₁₄ arylthio group, a halogen atom, a C₂₋₁₆ acylgroup, a C₂₋₁₇ alkoxycarbonyl group, a C₁₋₁₀ carbamoyl group or a C₁₋₁₀amide group, more preferably a C₁₋₁₀ alkoxy group, a C₆₋₁₀ aryloxygroup, a C₁₋₁₀ alkylthio group, a C₆₋₁₀ arylthio group, a chlorine atom,a C₂₋₁₁ alkoxycarbonyl group, a C₁₋₇ carbamoyl group, or a C₁₋₈ amidegroup, and particularly preferably a C₁₋₈ alkoxy group, a C₁₋₈ alkylthiogroup, a C₆₋₁₀ arylthio group, a C₃₋₉ alkoxycarbonyl group, or achlorine atom.

[0022] However, if m=1 and p≠0, the substituent represented by R¹ isparticularly preferably a C₂₋₁₆ alkyl group, a C₆₋₁₄ aryl group, a C₇₋₁₅aralkyl group, a C₁₋₁₆ alkoxy group, a C₆₋₁₄ aryloxy group, a C₂₋₁₇alkoxycarbonyl group, a C₁₋₁₀ carbamoyl group, a C₁₋₁₀ amide group, aC₂₋₁₇ acyloxy group, a C₂₋₁₆ acyl group, or a halogen atom.

[0023] A substituent represented by R¹ or R² may have a furthersubstituent, and examples of the further substituent in this caseinclude those enumerated above as substituents represented by R¹ or R².Further, R¹ may be a divalent or trivalent linking group, with which aplurality of the aromatic ring B may be substituted. In this case, thearomatic rings B substituted with R¹ may be the same as each other ordifferent.

[0024] Among the compounds represented by the general formula (I) above,the 1,2,3-triazole compounds represented by the following generalformula (I-A) are more preferable.

[0025] in which: h and k each independently represents an integer from 1to 3; R³ and R⁴ represent substituents; and r and s represent integersfrom 0 to 3. If h=1 and r≠0, R³ represents a substituent selected from agroup consisting of a C₂₋₁₆ alkl group, a C₆₋₁₄ aryl group, a C₇₋₁₅aralkyl group, a C₁₋₁₆ aloxy group, a C₆₋₁₄ arloxy group, a C₂₋₂₀ acylgroup, a C₂₋₁₇ alkoxycarbonyl group, a C₁₋₁₀ carbamoyl group, a C₁₋₁₀amide group, a C₂₋₁₇ acyloxy group, and a halogen atom.

[0026] The 1,2,3-triazole compounds represented by the general formula(I-A) are compounds whose benzene ring has been substituted at leastwith a hydroxyl group and the nitrogen atom at the 2-position in a1,2,3-benzotriazolyl group.

[0027] In the general formula (I-A), h is a number of1,2,3-benzotriazolyl groups. h is an integer from 1 to 3, preferably 1or 2, and particularly preferably 2. k is a number ofhydroxyl groups. kis an integer from 1 to 3, and preferably equals to h. Preferably, a1,2,3-benzotriazolyl group and hydroxyl group with which the benzenering is substituted are adjacent to each other.

[0028] In the general formula (I-A), R³ is a substituent on the benzenering, and R⁴ is a substituent on the 1,2,3-benzotriazole ring. r is anumber of substituent R³ groups. r is an integer from 0 to 3, preferably1 or 2, and particularly preferably 1. s is a number of substituent R⁴groups. s is an integer from 0 to 3, preferably 1 or 2, and particularlypreferably 1.

[0029] In the general formula (I-A), examples of the substituentsrepresented by R³ and R⁴ include those enumerated above as substituentsrespectively represented by R¹ and R² in the general formula (I). Thisalso applies to substituent preferences.

[0030] However, if h=1 and r≠0, the substituent represented by R³ isparticularly preferably a C₂₋₁₆ alkyl group, a C₆₋₁₄ aryl group, a C₇₋₁₅aralkyl group, a C₁₋₁₆ alkoxy group, a C₆₋₁₄ aryloxy group, a C₂₋₁₇alkoxycarbonyl group, a C₁₋₁₀ carbamoyl group, a C₁₋₁₀ amide group, aC₂₋₁₇ acyloxy group, a C₂₋₁₆ acyl group, or a halogen atom.

[0031] A substituent represented by R³ or R⁴ may have a furthersubstituent, and examples of the further substituent in this caseinclude those enumerated above as substituents represented by R¹ or R².Further, R³ may be a divalent or trivalent linking group, with which aplurality of benzene rings may be substituted. In this case, theplurality of benzene rings substituted with R³ may be substituted withdifferent substituents from each other.

[0032] Among the compounds represented by the general formula (I-A)above, the 1,2,3-triazole compounds represented by the following generalformula (I-B) are particularly preferable.

[0033] in which: R⁵ and R⁶ each independently represents a substituentselected from a group consisting of a C₁₋₂₀ linear or cyclic alkylgroup, a C₆₋₈ aryl group, a C₇₋₁₉ aralkyl group, and a 5- or 6-memberdheterocyclic group; R⁷ represents a substituent selected from a groupconsisting of a hydrogen atom, a halogen atom, a C₁₋₂₀ linear or cyclicalkyl group, a C₆₋₁₈ aryl group, a C₇₋₁₉ aralkyl group, a C₂₋₂₀ acylgroup, a C₁₋₂₀ alkoxy group, a C₂₋₂₀ alkoxycarbonyl group, and a C₁₋₁₇carbamoyl group; and R⁸ represents a substituent selected from a groupconsisting of a hydrogen atom, a halogen atom, a hydroxyl group, a C₁₋₂₀alkoxy group, and a C₂₋₂₀ acyloxy group. Each substituent represented byR⁷ and R⁸ may be linked together to form a ring.

[0034] In the general formula (I-B), the substituent represented by R⁵and R⁶ each independently is preferably a C₁₋₁₆ linear or cyclic alkylgroup, or a C₆₋₁₄ aryl group, more preferably a C₁₋₁₀ linear alkyl groupor phenyl group.

[0035] In the general formula (I-B), the substituent represented by R⁷is preferably a hydrogen atom, a C₁₋₁₆ linear alkyl group, a C₂₋₁₁ acylgroup, a C₁₋₁₆ alkoxy group, a C₂₋₁₁ alkoxycarbonyl group, or a C₁₋₁₀carbamoyl group, more preferably a C₂₋₁₁ acyl group, a C₁₋₁₆ alkoxygroup, or a C₂₋₁₁ alkoxycarbonyl group.

[0036] In the general formula (I-B), the substituent represented by R⁸is preferably a hydrogen atom, a hydroxyl group, or a C₁₋₁₆ alkoxygroup, more preferably a hydrogen atom or a hydroxyl group.

[0037] In the general formula (I-B), a substituent represented by R⁵,R⁶, R⁷ or R⁸ may have a further substituent, and examples of the furthersubstituent in this case include those enumerated above as substituentsrepresented by R¹ or R² in the general formula (I).

[0038] Compounds represented by the general formula (I), (I-A) or (I-B)may be bound to one another directly or indirectly at arbitrarypositions to form a multimer, and the respective units in this case maybe the same as each other or different. When the units are bound to oneanother directly or indirectly at an arbitrary position to form amultimer, they may be bound via a substituent represented by R¹ or R³,serving as a linking group. Further, they may be bound to a polymerchain such as polystyrene, polymethacrylate, polyvinyl alcohol,cellulose or the like.

[0039] Below, preferable examples of the 1,2,3-triazole compounds usedin the present invention are enumerated, but these are not intended tolimit the present invention.

[0040] The 1,2,3-triazole compounds used in the present invention can besynthesized by methods described or cited in, for example, JapanesePatent Application Publication (JP-B) No.54-41038, JP-B 60-14062, JP-B2-33709, Japanese Patent Nos. 2,858,940 and 2,864,468, British PatentNo. 1,239,258, U.S. Pat. No. 4,587,346, Polymer, Vol. 26, p. 1288(1985), Monatsh. Chem. 112, 1279 (1981), and the like (or by analogousmethods). 1,2,3-triazole compounds commercially available as coatings orpolymer stabilizers may also be used.

[0041] The 1,2,3-triazole compounds may be used singly or incombination. Further, a 1,2,3-triazole compound may be used incombination with another coloring compound serving as a recordingmaterial. Coloring compounds which can be used in such combinationinclude, for example, cyanine type dyes, oxonol type dyes, azo metalcomplexes, phthalocyanine type dyes, pyrylium type dyes, thiopyryliumtype dyes, azulenium type dyes, squarylium type dyes, naphthoquinonetype dyes, triphenyl methane type dyes, and triaryl methane dyes.

[0042] The optical information recording medium of the present inventionis not particularly limited insofar as it has a recording layercontaining a 1,2,3-triazole compound on a substrate, and the presentmedium can be applied in optical information recording media of variousstructures. The optical information recording medium of the presentinvention can be constituted such that, for example, a recording layer,a light-reflective layer and a protective layer are arranged in thisorder on a disk-shaped substrate having a pre-groove formed thereon witha predetermined track pitch. Hereinafter, a structure of an opticalinformation recording medium is described in detail by reference to aprocess of manufacturing an optical information recording medium havinga recording layer, a light-reflective layer and a protective layer inthis order on a disk-shaped substrate.

[0043] The substrate for the optical information recording medium of thepresent invention can be freely selected from a wide variety ofmaterials used as substrates for conventional optical informationrecording media. Examples of the substrate material include glass,polycarbonate, acrylic resins such as polymethyl methacrylate, vinylchloride-based resins such as polyvinyl chloride and vinyl chloridecopolymers, epoxy resins, amorphous polyolefins and polyester. Asnecessary, these materials may be used in combination. These materialscan be used as films or rigid substrates. Among the above materials,polycarbonate is preferable from the viewpoint of moisture resistance,dimensional stability and price.

[0044] The optical information recording medium of the present inventionpreferably uses a substrate having a pre-groove formed thereon with atrack pitch which is narrower than for a CD-R or DVD-R, to achieve ahigher recording density. For the optical information recording mediumof the present invention, the track pitch is preferably in the range of0.2 to 0.8 μm, more preferably 0.25 to 0.50 μm and further preferably0.30 to 0.35 μm. The depth of the pre-groove is preferably in the rangeof 0.020 to 0.18 μm, more preferably 0.025 to 0.075 μm and particularlypreferably 0.025 to 0.045 μm.

[0045] For the purpose of improving flatness, improving adhesion andpreventing deterioration of the recording layer, the surface of thesubstrate on which the recording layer is to be arranged may be providedwith an undercoat layer. Example materials of the undercoat layerinclude polymeric materials such as polymethyl methacrylate, acrylicacid-methacrylic acid copolymers, styrene-maleic anhydride copolymers,polyvinyl alcohols, N-methylol acrylamide, styrene-vinyl toluenecopolymers, chlorosulfonated polyethylene, nitrocellulose, polyvinylchloride, chlorinated polyolefin, polyester, polyimide, vinylacetate-vinyl chloride copolymers, ethylene-vinyl acetate copolymers,polyethylene, polypropylene and polycarbonate, as well as surfacemodifiers such as silane coupling agents. The undercoat layer can beformed by dissolving or dispersing the above material in a suitablesolvent to prepare a coating solution and then applying this coatingsolution onto the surface of the substrate by a coating method such asspin coating, dip coating or extrusion coating. The thickness of theundercoat layer is generally in the range of 0.005 to 20 μm, andpreferably in the range of 0.01 to 10 μm.

[0046] The recording layer can be formed by dissolving the1,2,3-triazole compound and additives such as a binder in a solvent toprepare a coating solution, applying this coating solution onto thesurface of the substrate to form a coating thereon, and then drying.

[0047] Examples of the solvent for use in the coating solution includeesters such as butyl acetate, ethyl lactate and cellosolve acetate;ketones such as, methyl ethyl ketone, cyclohexanone and methyl isobutylketone; chlorinated hydrocarbons such as dichloromethane,1,2-dichloroethane and chloroform; amides such as dimethyl formamide;hydrocarbons such as methyl cyclohexane; ethers such as tetrahydrofuran,ethyl ether and dioxane; alcohols such as ethanol, n-propanol,isopropanol and n-butanol diacetone alcohol; fluorine type solvents suchas 2,2,3,3-tetrafluoropropanol; and glycol ethers such as ethyleneglycol monomethyl ether, ethylene glycol monoethyl ether and propyleneglycol monomethyl ether. These solvents can be used singly or incombination, in consideration of solubility of a dye to be used.Depending on objectives, various additives such as antioxidants, UVabsorbers, plasticizers, lubricants and the like may further be added tothe coating solution.

[0048] In the case where a binder is used, examples of the binderinclude natural organic polymers such as gelatin, cellulose derivatives,dextran, rosin and rubber, and synthetic organic polymers such asinitial condensates of thermosetting resins, including: hydrocarbon typeresins such as polyethylene, polypropylene, polystyrene andpolyisobutylene; vinyl type resins such as polyvinyl chloride,polyvinylidene chloride, and polyvinyl chloride-polyvinyl acetatecopolymers; acrylic resins such as methyl polyacrylate and methylpolymethacrylate; polyvinyl alcohol; chlorinated polyethylene; epoxyresins; butyral resins; rubber derivatives; phenol-formaldehyde resinsand the like. If the binder is used in combination as a material in therecording layer, the amount of the binder used is generally in the rangeof 0.01 to 50 parts per part of the dye (ratio by weight), andpreferably in the range of 0.1 to 5 parts (ratio by weight). Theconcentration of the dye in the coating solution thus prepared isgenerally in the range of 0.01 to 10% by weight, and preferably 0.1 to5% by weight.

[0049] The coating method includes spraying, spin-coating, dipping, rollcoating, blade coating, doctor rolling, screen printing, etc. Therecording layer may be a single layer or multiple layers. The thicknessof the recording layer is generally in the range of 20 to 500 nm,preferably in the range of 30 to 300 nm and more preferably in the rangeof 50 to 100 nm.

[0050] To improve the light resistance of the recording layer, therecording layer can contain various discoloration inhibitors. As thediscoloration inhibitor, a singlet oxygen quencher is generally used.The singlet oxygen quencher may be one described in literature such asprior patent specifications and the like. Examples thereof include thosedescribed in JP-A 58-175693, JP-A 59-81194, JP-A 60-18387, JP-A60-19586, JP-A 60-19587, JP-A 60-35054, JP-A 60-36190, JP-A 60-36191,JP-A 60-44554, JP-A 60-44555, JP-A 60-44389, JP-A 60-44390, JP-A60-54892, JP-A 60-47069, JP-A 63-209995, JP-A 4-25492, JP-B 1-38680,JP-B 6-26028, German Patent No. 350399, and the Journal of the JapaneseChemical Society (page 1141 in the October 1992 issue). Preferableexamples of the singlet oxygen quencher include compounds represented bythe general formula (II):

[0051] in which R²¹ represents an alkyl group which may have asubstituent, and Q⁻ represents an anion.

[0052] In the general formula (II), R²¹ is generally an optionallysubstituted C₁₋₈ alkyl group, and preferably an unsubstituted C₁₋₆ alkylgroup. Substituents on the alkyl group include a halogen atom (e.g., For Cl), an alkoxy group (e.g., methoxy or ethoxy), an alkylthio group(e.g., methylthio or ethylthio), an acyl group (e.g., acetyl orpropionyl), an acyloxy group (e.g., acetoxy or propionyloxy), a hydroxylgroup, an alkoxycarbonyl group (e.g., methoxycarbonyl orethoxycarbonyl), an alkenyl group (e.g., vinyl) and an aryl group (e.g.,phenyl or naphthyl). Among these, the halogen atom, the alkoxy group,the alkylthio group and the alkoxycarbonyl group are preferable.Preferable examples of the Q⁻ anion include ClO₄ ⁻, AsF₆ ⁻, BF₄ ⁻ andSbF₆ ⁻.

[0053] Examples of compounds represented by the general formula (II) arelisted in Table 1. TABLE 1 Compound No. R²¹ Q⁻ II-1 CH₃ ClO₄ II-2 C₂H₅ClO₄ II-3 n-C₃H₇ ClO₄ II-4 n-C₄H₉ ClO₄ II-5 n-C₅H₁₁ ClO₄ II-6 n-C₄H₉SbF₆ ⁻ II-7 n-C₄H₉ BF₄ ⁻ II-8 n-C₄H₉ AsF₆ ⁻

[0054] The amount of the discoloration inhibitor such as a singletoxygen quencher is usually in the range of 0.1 to 50% by weight,preferably in the range of 0.5 to 45% by weight, more preferably in therange of 3 to 40% by weight and particularly preferably in the range of5 to 25% by weight, relative to the amount of dye.

[0055] For the purpose of improving reflectance during reproduction ofinformation, the recording layer is preferably provided with alight-reflective layer thereon. A light-reflective material to be amaterial of the light-reflective layer is a material showing highreflectance of lasers, and examples thereof include metals such as Mg,Se, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd,Ir, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Si, Ge, Te, Pb, Po, Sn and Bi,semimetals thereof, and stainless steel. These materials may be usedsingly or may be combined for use as an alloy. Of these materials, Cr,Ni, Pt, Cu, Ag, Au, Al and stainless steel are preferable. Au metal, Agmetal, Al metal and alloys thereof are particularly preferable, and Agmetal, Al metal or an alloy thereof is most preferable. Thelight-reflective layer can be formed on the substrate or the recordinglayer by, for example, depositing, sputtering or ion-plating the abovelight-reflective material. The thickness of the light-reflective layeris generally in the range of 10 to 300 nm, and preferably in the rangeof 50 to 200 nm.

[0056] For the purpose of physically and chemically protecting therecording layer and the like, the light-reflective layer or therecording layer is preferably provided with a protective layer thereon.If the optical information recording medium has the same structure as aDVD-R type medium, that is, a structure in which two substrates arelaminated with the recording layer arranged therebetween, it may not benecessary to provide the medium with a protective layer. A material usedin the protective layer includes, for example, an inorganic materialsuch as SiO, SiO₂, MgF₂, SnO₂, Si₃N₄ or the like, or an organicmaterials such as a thermoplastic resin, thermosetting resin, UV curingresin or the like. For example, a film obtained by extrusion of aplastic may be laminated onto the reflective layer via an adhesive toform the protective layer. Alternatively, the protective layer may beformed by a method such as vacuum deposition, sputtering or coating. Ifa thermoplastic or thermosetting resin is used, the resin may bedissolved in a suitable solvent to prepare a coating solution which isthen applied and dried to form the protective layer. If a UV curingresin is used, the resin may be applied directly or a coating solutionthereof dissolved in a suitable solvent may be applied and dried, andthen cured by irradiation with UV rays to form the protective layer.Depending on objectives, various additives such as antistatic agents,antioxidants, UV absorbers and the lile may be added to these coatingsolutions. The thickness of the protective layer is generally in therange of 0.1 μm to 1 mm. By the process described above, it is possibleto produce a laminate consisting of the recording layer, thelight-reflective layer and the protective layer arranged on thesubstrate or a laminate consisting of the light-reflective layer, therecording layer and the protective layer arranged on the substrate.

[0057] Using the optical information recording medium described above,the information recording method of the present invention is conducted,for example, as follows. First, while the optical information recordingmedium is rotated at a constant linear velocity (1.2 to 1.4 m/sec. inthe case of CD format) or at a constant angular velocity, the recordingmedium is irradiated from the substrate side or the protective layerside with recording rays such as rays from a semiconductor laser. It isthought that, when irradiated with these rays, the recording layerabsorbs the rays to increase temperature locally, thus undergoing aphysical or chemical change (e.g., formation of pits) and changing theoptical characteristics at that portion to thereby record information.In the present invention, a semiconductor laser having an oscillationwavelength in the range of 390 to 550 nm is used as the recording ray.

[0058] Preferable light sources include a bluish-purple semiconductorlaser having an oscillation wavelength in the range of 390 to 415 nm, abluish-green semiconductor laser with a central oscillation wavelengthof 515 nm, and a bluish-purple SHG laser with a central oscillationwavelength of 425 nm, which includes an infrared semiconductor laserwith a central oscillation wavelength of 850 nm and a photoconductivewave-guide type wavelength conversion element (SHG). Among these, thebluish purple semiconductor laser or the SHG laser is particularlypreferably used. The information recorded in the manner described abovecan be reproduced by irradiating the substrate of the opticalinformation recording medium with laser rays, during rotation at thesame predetermined linear velocity, and detecting reflected rays.

[0059] The optical information recording medium of the presentinvention, similarly to a conventional DVD-R, can be structured suchthat two laminates, each consisting of a recording layer and a lightrecording layer arranged on a transparent disk-shaped substrate having apre-groove formed thereon with a predetermined track pitch, arelaminated with the recording layers on the inside. Further, the mediumcan be structured such that the above-described laminate and adisk-shaped protective substrate of the same shape as the laminate arelaminated with the recording layer on the inside. To produce thislaminated structure, for example, a transparent substrate having adiameter of 120±3 mm and a thickness of 0.6±0.1 mm is used, and thelight information recording medium after lamination is controlled tohave a thickness of 1.2±0.2 mm. A UV curing resin used in formation ofthe protective layer or a synthetic adhesive may be used for thislamination. Also, a double-coated tape can be used for lamination.

[0060] Further, the optical information recording medium of the presentinvention can be structured such that, for example, a light-reflectivelayer, a recording layer and a thin-film protective layer are arrangedin this order on a disk-shaped substrate having a pre-groove formedthereon with a predetermined track pitch. This optical informationrecording medium is provided with the thin-film protective layer at aside opposite to the substrate side, and the substrate has apredetermined thickness (1.2 mm for CD-R). For recording, this medium isirradiated with rays from the thin-film protective layer side, wherebybeam diameter of the irradiation laser rays can be minimized to achievehigh-density recording by short-wavelength rays having wavelengths of450 nm or less.

[0061] Preferably, the thin-film protective layer described above has athickness from 0.1 to 300 μm and is formed of a photo-setting resin orfilm-form resin. The thin-film protective layer may be arranged on therecording layer via an intermediate layer, an adhesive layer or thelike. The intermediate layer is provided for improving storage stabilityof the recording layer and improving adhesion between the recordinglayer and the thin-film protective layer. Examples of materials used inthe intermediate layer include inorganic materials such as SiO, SiO₂,MgF₂, SnO₂ and Si₃N₄. The intermediate layer can be formed by vacuumfilm formation, such as deposition or sputtering. The adhesive layerpreferably uses an adhesive containing a photo-setting resin. Forexample, a photo-setting resin or a coating solution thereof in asuitable solvent is applied onto the intermediate layer, then a resinfilm obtained by extrusion of a plastic is laminated onto the resultingcoating, and the resin film thus laminated is irradiated with rays tocure the coating, whereby the resin film can be stuck on theintermediate layer. Thus, the thin-film protective layer is formed.

EXAMPLES

[0062] Below, the present invention is described in more detail byreference to Examples, which are not intended to limit the presentinvention.

Example 1

[0063] Exemplified compound (1) was dissolved in methyl cyclohexane togive a recording layer-forming coating solution (concentration: 1 weight%). A recording layer (thickness at pre-groove: about 80 nm) was formedby applying this coating solution by spin coating onto the surface of apolycarbonate substrate (diameter, 120 mm; thickness, 0.6 mm) on which aspiral pre-groove (track pitch, 0.35 μm; groove width, 0.2 μm; groovedepth, 0.045 μm) had been formed by extrusion molding. Then, silver wassputtered onto the recording layer to form a light-reflective layer ofabout 100 nm thickness thereon. Further, a UV curing resin (SD318,produced by Dainippon Ink and Chemicals, Inc.) was applied onto thelight-reflective layer and cured by irradiation with UV rays to form aprotective layer of 7 μm in thickness thereon. By the process describedabove, an optical disk according to the present invention was obtained.

Examples 2 to 9

[0064] Optical disks according to the present invention were produced inthe same manner as in Example 1 except that the exemplified compoundslisted in Table 2 were used in place of the exemplified compound (1)(the amount of compound was not changed).

Comparative Examples 1 to 5

[0065] Comparative optical disks were produced in the same manner as in,Example 1 except that comparative coloring compounds A to E, shownbelow, were used in place of the exemplified compound (1) (the amount ofcompound was not changed) and 2,2,3,3-tetrafluoropropanol was used asthe coating solvent instead of methyl cyclohexane.

Comparative Compounds

[0066]

Evaluation of the Optical Disks

[0067] The thus prepared optical disks were recorded with a 14T-EFMsignal at a linear velocity of 3.5 m/sec., using a bluish-purplesemiconductor laser with an oscillation wavelength of 405 nm, and thenthe recorded signal was replayed. Modulation degree, groove reflectanceand sensitivity were measured at optimum power. The recording andrecording characteristics were evaluated using “DDU1000”, manufacturedby Pulstec Co., Ltd. Evaluation results are shown in Table 2. TABLE 2Coloring Reflectance compound at in the unrecorded Degree of recordingportion modulation Sensitivity layer (%) (%) (mW) Example 1  (1) 70 627.2 Example 2  (3) 68 59 7.3 Example 3  (6) 69 60 6.9 Example 4 (15) 7365 6.5 Example 5 (16) 72 66 6.6 Example 6 (17) 73 64 6.5 Example 7 (22)71 66 6.4 Example 8 (28) 67 58 7.5 Example 9 (35) 75 69 6.1 Comparative(A) 35 58 7.9 Example 1 Comparative (B) 36 41 9.7 Example 2 Comparative(C) 61 54 8.3 Example 3 Comparative (D) 55 56 8.8 Example 4 Comparative(E) Not measurable due to whitening of Example 5 the recording layer

[0068] As can be seen from the results in Table 2, the optical disks ofthe present invention containing the 1,2,3-triazole compound as therecording material in the recording layer (Examples 1 to 9), whencompared with the optical disks containing Comparative Compounds A to Das the recording material in the recording layer (Comparative Examples 1to 4), exhibited high reflectance, gave high degrees of modulation andhad high sensitivity when irradiated with a laser ray having a shortwavelength of 405 nm (a bluish-purple laser ray). Accordingly, it can beunderstood that the optical information recording medium according tothe present invention is capable of recording and regeneratinginformation by irradiation with a laser ray having a short wavelength of405 nm, and has excellent recording characteristics with respect to alaser ray with a short wavelength of 405 nm. Further, the optical diskcontaining Comparative Compound E, which had a group derived from1,3-dimethylbarbituric acid, in the recording layer could not be usedfor recording because of whitening of the recording layer, whereas theoptical disks of the present invention, which used the 1,2,3-triazolecompounds, could form transparent, stable recording layers.

[0069] The optical information recording medium of the present inventiondemonstrates the effects of being capable of recording and reproductionby irradiation with laser rays having wavelengths of 550 nm or less,particularly laser rays having wavelengths of 450 nm or less, which areshorter wavelengths than those of laser rays used in recording andreproduction of CD-R and DVD-R, and has excellent recordingcharacteristics with respect to exhibiting high reflectance for suchlaser rays and providing a high degree of modulation and highsensitivity.

[0070] By use of the optical information recording medium of the presentinvention, the information recording method of the present inventiondemonstrates the effects of being capable of high-density recording ofinformation and of recording large amounts of information by irradiationwith laser rays having wavelengths of 550 nm or less, particularly laserrays having wavelengths of 450 nm or less, which are shorter wavelengthsthan those of laser rays used in recording and reproduction of CD-R andDVD-R.

What is claimed is:
 1. An optical information recording mediumcomprising: a substrate; and a recording layer on the substrate which iscapable of recording information by irradiation with laser rays, therecording layer comprising a 1,2,3-triazole compound devoid of acondensate with 1,3-dimethylbarbituric acid.
 2. An optical informationrecording medium according to claim 1, wherein the 1,2,3-triazolecompound is represented by the following general formula I:

in which: A and B represent aromatic rings which may have substituents;in and n each independently represents an integer from 1 to 3; R¹ and R²represent substituents, and the substituent represented by R¹ is notderived from 1,3-dimethylbarbituric acid; and p and q represent integersfrom 0 to
 3. 3. An optical information recording medium according toclaim 1, wherein the 1,2,3-triazole compound is represented by thefollowing general formula I:

in which: A and B represent aromatic rings which may have substituents;m and n each independently represents an integer from 1 to 3; R¹represents a substituent on the aromatic ring B and R² represents asubstituent on the aromatic ring A; p and q represent integers from 0 to3; and, if m=1 and p≠0, R¹ represents a substituent selected from thegroup consisting of a C₂₋₁₆ alkyl group, a C₆₋₁₄ aryl group, a C₇₋₁₅aralkyl group, a C₁₋₁₆ alkoxy group, a C₆₋₁₄ aryloxy group, a C₂₋₁₇alkoxycarbonyl group, a C₁₋₁₀ carbamoyl group, a C₁₋₁₀ amide group, aC₂₋₁₇ acyloxy group, a C₂₋₂₀ acyl group, and a halogen atom.
 4. Anoptical information recording medium according to claim 1, wherein the1,2,3-triazole compound is represented by the following general formulaI-A:

in which: h and k each independently represents an integer from 1 to 3;R³ and R⁴ represent substituents; r and s represent integers from 0 to3; and, if h=1 and r≠0, R³ represents a substituent selected from thegroup consisting of a C₂₋₁₆ alkyl group, a C₆₋₁₄ aryl group, a C₇₋₁₅aralkyl group, a C₁₋₁₆ alkoxy group, a C₆₋₁₄ aryloxy group, a C₂₋₁₇alkoxycarbonyl group, a C₁₋₁₀ carbamoyl group, a C₁₋₁₀ amide group, aC₂₋₁₇ acyloxy group, a C₂₋₂₀ acyl group, and a halogen atom.
 5. Anoptical information recording medium according to claim 1, wherein the1,2,3-triazole compound is represented by the following general formulaI-B:

in which: R⁵ and R⁶ each independently represents a substituent selectedfrom a group consisting of a C₁₋₂₀ linear or cyclic alkyl group, a C₆₋₁₈aryl group, a C₇₋₉ aralkyl group, and a 5- or 6-memberd heterocyclicgroup; R⁷ represents a substituent selected from a group consisting of ahydrogen atom, a halogen atom, a C₁₋₂₀ linear or cyclic alkyl group, aC₆₋₁₈ aryl group, a C₇₋₁₉ aralkyl group, a C₂₋₂₀ acyl group, a C₁₋₂₀alkoxy group, a C₂₋₂₀ alkoxycarbonyl group, and a C₁₋₁₇ carbamoyl group;R⁸ represents a substituent selected from a group consisting of ahydrogen atom, a halogen atom, a hydroxyl group, a C₁₋₂₀ alkoxy group,and a C₂₋₂₀ acyloxy group; and each substituent represented by R⁷ and R⁸may be linked together to form a ring.
 6. An optical informationrecording medium according to claim 1, wherein the substrate is atransparent disk-shaped substrate having a pre-groove formed at at leastone surface thereof with a track pitch of 0.2 to 0.8 μm, and therecording layer is provided on the surface of the substrate at which thepre-groove is formed.
 7. An optical information recording mediumaccording to claim 1, further comprising at least one of alight-reflective layer formed of a metal and a protective layer.
 8. Aninformation recording method comprising the steps of: providing anoptical information recording medium comprising, on a substrate, arecording layer capable of recording information by irradiation withlaser rays, the recording layer comprising a 1,2,3-triazole compounddevoid of a condensate with 1,3-dimethylbarbituric acid; and irradiatingthe optical information recording medium with a laser having awavelength of at most 550 nm for recording information.
 9. Aninformation recording method according to claim 8, wherein the1,2,3-triazole compound is represented by the following general formulaI:

in which: A and B represent aromatic rings which may have substituents;m and n each independently represents an integer from 1 to 3; R¹ and R²represent substituents, and the substituent represented by R¹ is notderived from 1,3-dimethylbarbituric acid; and p and q represent integersfrom 0 to
 3. 10. An information recording method according to claim 8,wherein the 1,2,3-triazole compound is represented by the followinggeneral formula I:

in which: A and B represent aromatic rings which may have substituents;m and n each independently represents an integer from 1 to 3; R¹represents a substituent on the aromatic ring B and R² represents asubstituent on the aromatic ring A; p and q represent integers from 0 to3; and, if m=1 and p≠0, R¹ represents a substituent selected from thegroup consisting of a C₂₋₁₆ alkyl group, a C₆₋₁₄ aryl group, a C₇₋₁₅aralkyl group, a C₁₋₁₆ alkoxy group, a C₆₋₁₄ aryloxy group, a C₂₋₁₇alkoxycarbonyl group, a C₁₋₁₀ carbamoyl group, a C₁₋₁₀ amide group, aC₂₋₁₇ acyloxy group, a C₂₋₂₀ acyl group, and a halogen atom.
 11. Aninformation recording method according to claim 8, wherein the1,2,3-triazole compound is represented by the following general formulaI-A:

in which: h and k each independently represents an integer from 1 to 3;R³ and R⁴ represent substituents; r and s represent integers from 0 to3; and, if h=1 and r≠0, R³ represents a substituent selected from thegroup consisting of a C₂₋₁₆ alkyl group, a C₆₋₁₄ aryl group, a C₇₋₁₅aralkyl group, a C₁₋₁₆ alkoxy group, a C₆₋₁₄ aryloxy group, a C₂₋₁₇alkoxycarbonyl group, a C₁₋₁₀ carbamoyl group, a C₁₋₁₀ amide group, aC₂₋₁₇ acyloxy group, a C₂₋₂₀ acyl group, and a halogen atom.
 12. Aninformation recording method according to claim 8, wherein the1,2,3-triazole compound is represented by the following general formulaI-B:

in which: R⁵ and R⁶ each independently represents a substituent selectedfrom a group consisting of a C₁₋₂₀ linear or cyclic alkyl group, a C₆₋₁₈aryl group, a C₇₋₁₉ aralkyl group, and a 5- or 6-memberd heterocyclicgroup; R⁷ represents a substituent selected from a group consisting of ahydrogen atom, a halogen atom, a C₁₋₂₀ linear or cyclic alkyl group, aC₆₋₁₈ aryl group, a C₇₋₁₉ aralkyl group, a C₂₋₂₀ acyl group, a C₁₋₂₀alkoxy group, a C₂₋₂₀ alkoxycarbonyl group, and a C₁₋₁₇ carbamoyl group;R⁸ represents a substituent selected from a group consisting of ahydrogen atom, a halogen atom, a hydroxyl group, a C₁₋₂₀ alkoxy group,and a C₂₋₂₀ acyloxy group; and each substituent represented by R⁷ and R⁸may be linked together to form a ring.
 13. An information recordingmethod according to claim 8, wherein the substrate of the opticalinformation recording medium is a transparent disk-shaped substratehaving a pre-groove formed at at least one surface thereof with a trackpitch of 0.2 to 0.8 μm, and the recording layer is provided on thesurface of the substrate at which the pre-groove is formed.
 14. Aninformation recording method according to claim 8, wherein the opticalinformation recording medium further includes at least one of alight-reflective layer formed of a metal and a protective layer.